The invention concerns an inlet for a separator (separator tank) in a process plant, for example a plant for processing a fluid consisting of oil, water and/or gas.
The inlet arrangement in a separator in a process plant usually has several purposes. First, the inlet reduces the impulse to incoming fluid to prevent the inlet flow from disturbing the steady flow conditions required in the separator. Second, the inlet prevents sand or similar material in the process flow from being deposited in places where this is undesirable. Thirdly, the inlet prepares the process flow so that the conditions for good separation are optimal.
In practice, impulse reduction is usually the guiding factor for the design of an inlet in a separator. A widely known impulse reduction solution is based on the use of a flow interruption plate arranged just outside the separator inlet. The fluid flow meets the plate and is spread outwards and possibly backwards if the plate is curved. Another impulse reduction solution is based on the use of a U-shaped pipe in connection with the inlet to xe2x80x9creturnxe2x80x9d the flow towards the separator wall. A third solution is based on the use of a T-pipe section in connection with the inlet to interrupt the fluid flow and steer it sideways.
However, all of these solutions create a greater or lesser degree of spray, agitation and disturbance to the surface of the fluid, which means that the conditions for good separation are not achieved or are poor. If the fluid supply flow consists of oil and water, large shear stresses, for example as a result of pressure loss across a valve or sudden changes of speed, can lead to the oil and/or water being turned into small drops and a so-called emulsion being formed. In its simplest form, the emulsion is either oil-in-water (oil drops in water) or water-in-oil (water drops in oil). Surfactants in the oil can stabilize the emulsion and make it difficult to separate the oil and water. Water-in-oil emulsions are considered to be more difficult to break down than oil-in-water emulsions.
If the fluid supply flow contains free gas in addition to oil and water, shear stresses to which the fluid supply flow is exposed can lead to the formation of small gas bubbles which are mixed with the fluid phases. These gas bubbles can have an emulsion-stabilizing effect like the surfactants in oil.
The present invention represents an inlet to a separator in which the fluid inlet flow is not exposed to unnecessarily large shear stresses (plunging, sudden changes of speed), and in which free gas which may be present in the fluid supply flow is released before the fluid flow is exposed to shear stresses. Moreover, the present invention represents an inlet which produces steady flow conditions in the separator and prevents any sand or other particulate contaminants from being deposited in places where this is undesirable.
The present invention is characterized in that the separator inlet is designed as a spiral channel open at the top in a channel housing. The fluid flows in tangentially and flows out through a central outlet in the housing downwards.